Xerographic development apparatus



Nov. 10, 1959 R. E. HAYFORD ET AL 2,

XEROGRAPHIC DEVELOPMENT APPARATUS Filed Sept. 16, 1954 4 Sheets-Sheet 1HIGH VOLTAGE 5 I5 SOURCE l3 2 DEVELOPER CLOUD SUPPLY DEVELOPER SUPPLY INVEN TOR. RICHARD E. HAYFORD HERBERT E. CRUMRINE ATTORNEY Nov. 10, 1959R. E. HAYFORD ET AL 2,911,944

XEROGRAPHIC DEVELOPMENT APPARATUS 4 Sheets-Sheet 3 Filed Sept. 16. 1954FIG. 4

w w Q Q FIG.5

INVENTOR RICHARD E. HAYFORD HERBERT E. CRUMRINE ATTORNEY Nov. 10, 1959Filed Sept. 16, 1954 R. E. HAYFORD ET AL XEROGRAPHIC DEVELOPMENTAPPARATUS 4 Sheets-Sheet 4 INVENTOR.

RICHARD E, HAYFORD HE BERT E, CRUMRINE ATTORNEY United States PatentXEROGRAPHIC DEVELOPMENT APPARATUS Richard E. Hayford, Perinton, andHerbert E. Crumrine,

Rochester, N.Y., assignors to Haloid Xerox Inc., a corporation of NewYork Application September 16, 1954, Serial No. 456,538

6 Claims. (Cl. 118-637) This invention relates to xerography and moreparticularly to an electrode used in the development process.

In the art of xerography images are formed on xerographic plates. Theplates are composed of photoconductive insulating material overlying aconductive backing member. Plates are sensitized by placing a uniformelectrostatic charge on the photoconductive insulating layer while theplate is kept in darkness, and a latent image is formed on the surfaceof the insulating layer by exposing this layer, while sensitive, to alight pattern. Areas of this layer struck by light become conductive anddissipate the electrostatic charges on the surface by allowing them toflow to the conductive backing member. Areas of the sensitivephotoconductive insulator not exposed to light continue to act asinsulators and retain the electrostatic charge on the surface.

The latent image which is formed on the surface of the photoconductiveinsulator is composed of electrostatic charges in image formation. Thiselectrostatic image pattern may be developed by bringing particles whichare charged opposite in sign to the electric charge of the patternitself into contact with the surface carrying the charge pattern or thepattern may be otherwise utilized. A developed image on the surface of aplate may be transferred to sheets or webs through the use ofelectrostatics or other methods known to the art and may be therepermanently aifixed or, it may be allowed to remain on the plate forviewing and the like.

Xerography, as described above, may be adapted for automatic typeoperation. For example, the xerographic plate may be made toautomatically progress through the different stages of operationnecessary to produce the developed image which may then be automaticallytrans ferred or otherwise utilized. This form of automatic operation mayalso be adapted for continuous automatic operation by repeating thexerographic image producing cycle automatically.

A problem which has been encountered in automatic continuously operatingmachines involves an electrode used during the development stage. Thiselectrode, which will be referred to in this application as thedevelopment electrode, is positioned parallel to the photoconductiveinsulating layer during development.

Basic to the use of the development electrode is the desire to reproducecopies of the original image of high quality and without distortion.Electrostatic lines of force exist between the electrostatic charges onthe photoconductive insulating layer and areas of different chargepotential. When large areas carrying electrostatic charges exist thelines of force which are present due to charges in the central area ofthe large area tend to run inward through the photoconductive insulatinglayer to the conductive backing member which is the nearest surfacecarrying a different potential. Lines of force running fromelectrostatic charges near the external boundaries of this large areawill tend to extend outward and around the outside border of the largearea at which point their paths will extend inward through thephotoconduc five insulating layer to the conductive backing member.Development of such an electrostatic latent image creates depositionwhich relates to the paths taken by the electrostatic lines of force ordevelopment of the electrostatic fields. Therefore, development of alarge area as has just been described will reproduce copies with hollowcenters and emphasized edges. To prevent such development a surface ispositioned at a slight distance from the photoconductive insulatinglayer during development. This surface, the development electrode, iscomposed of a conductive material and is usually either biased slightlyor maintained at about the same potential as the plate backing member.Such an equipotential surface will cause an increase in the lines offorce extending outwardly from the plate member creating electrostaticfields which when developed will produce distortion free and fringe freehigh quality copy.

It is an object of this invention to improve the art of xerography byproviding new means, methods and apparatus which relate to thedevelopment electrode.

During development of the electrostatic latent image on thephotoconductive insulating surface fine powder particles are broughtinto the field of influence of the charges on the surface and aredeposited on charged areas. The development electrode which is spaced ata slight distance from this sensitive layer, at a distance which iswithin the field of influence of the electrostatic charges on the layersurface, tends to build up on its surface a coating of developermaterial. While this coating remains thin the image which is developedis generally not affected. However, a coating of developer material onthe development electrode interposes a new surface between the sensitivelayer and the development electrode and if the particles carryelectrostatic charge, this coating may effectively change the biaspotential on the electrode which substantially decreases beneficialaspects of the development electrode during development of theelectrostatic image and this coating also adds new uncontrol lableproblems. The lack of control which follows heavy deposition is to someextent also attributed to the fact that the coating which forms isgenerally uneven and follows unknown and different patterns. A heavycoating may drop agglomerates of developer powder to the plate surfaceresulting in a nonuniform distorted development of the electric imagepattern. Also, such a coating may cause irregular and uncontrolled flowpatterns of the developer material being presented to the plate surfacewhich will cause streaking of the developed image.

-It is, therefore, an object of this invention to provide means, methodsand apparatus to control the amount of material allowed to remaindeposited on the development electrode.

In continuously operating automatic machines development is constantlytaking place in that a new portion of a latent image is continuouslybeing presented to the development zone for development purposes.Therefore, it becomes necessary to present to the development zone adevelopment electrode with a minimum coating of developer particles tofacilitate high quality true reproductions in a continuously operatingautomatic machine.

It is, therefore, another object of this invention to provide means andmethods to control and limit the amount of material allowed to depositand remain on effective areas of the development electrode used in amachine adapted for continuous operation.

. It is another object of this invention to provide apparatus to controland limit the amount of material allowed to deposit on effective areasof the development electrode used in a machine adapted for continuousopera tion.

Briefly, this invention embodies a development electrode of slightlymore than twice the width of the xerogia'phio plate which constantlymoves back and forth across the width or the xerographic plate. The pathof travel of the development electrode extends just slightly more thanhalf of the electrode outward from one edge of the photoconductiveinsulating layer and then from the other edge. Brushes extending outwardfrom the sensitive layer constantly move up and down along the length ofthe development electrode not directly above the sensitive layer orareas extending outward from the edge of this layer thereby brushingclean areas of the development electrode.

It is another object of this invention to provide apparatusto'cleain'all areasof a development electrode used in a machine adaptedfor continuous operation during each successive cycle of movement of thedevelopment electrode.

It is yet another object of this invention to provide means and methodsto clean all areas of a development electrode used in a machine adaptedfor continuous operation during each successive cycle of movement of thedevelopment electrode.

In machines adapted for continuous operation wherein the xerog'raphicplate is in the shape of a cylindrical drum, a development electrode ofthe same shape as the portion of the drum it is positioned over would berequired. This form or shape of a development electrode is required toprovide equal spacing of the electrode from the photoconductiveinsulating layer. Cleaning means, as for example, brushes which sweepthe deposited developer from the development electrode must follow thecircumference of the development electrode in order to properly cleanand condition the electrode for development purposes.

Iti's an additional object of this invention to provide apparatus forcleaning an internally cylindrically shaped development electrode.

It is yet a further object of this invention to provide means andmethods for cleaning a shaped development electrode.

Other objects and advantages of this invention will be apparent in viewof the following description considered in the light of the attacheddrawings wherein,

Figure 1 illustrates one embodiment of an automatic electrophotographicdevice adapted for continuous operation;

Figure 2 is a side view of one embodiment of the development section ofthe apparatus shown in Figure'l;

Figure 3 is a front view of one embodiment of the development electrodeand its driving mechanism;

Figure 4 is a side View of one embodiment of the meansprovided toposition and guidethe development electrode through its cycles;

Figure 5 is a top view of one embodiment of the-development electrodecleaning means; and

Figure 6 illustrates one embodiment of the driving mechanism for thecleaning means.

Referring -more specifically to the drawings,-in Figure 1 an embodimentof a continuously operating xerographic apparatus is shown. Thexerographic plate is in this instance formed in the shape of a rotatingdrum generally designated 10 and is composed of conductive backingmember 11 and photoconductive insulating layer 12. Conductive backingmember 11 is, as indicated, heldat a groundpotential. A uniformelectrostatic charge is placed on 'layer'12 by corona dischargeelectrode 13 which is supplied from high voltage source 15 at theareagenerally designated 25. An image 16 on a surface moving at a properlinear speed is illuminated by lamps 17 and-is projected from betweenslit 19 through lens 18 atexposure station generally designated whereatthe electrostatic latentimage'isformed on sensitive layer 12.At'position 21-'deve1opm'ent' of the electrostatic latent image takesplace. Developer cloud supply 22 supplies a cloud of developer'particles 'in air to the area between layer 12 and developmentelectrode 2 3 where development of the -within its grooves causesmovement of guide member 46 and-so: movement of development electrode 23which is attached'to guide'member 46 until pin'51 reachesone endelectrostatic latent image on layer 12 takes place. At the areagenerally designated 26 transfer of the developed image from layer 12takes place. Roll 27 supplies a continuously fed web 28 under roller 30and into contact with layer 12 whereat adhesive form of transfer occursby using a web 28 having an adhesive coating on one surface thereof andapplying proper pressure with roller 30. It is to be understood, ofcourse, that other types of transfer may be used, such as coronatransfer, and this inventionis intended to include the other forms oftransfer within its scope. The Web, optionally, is next fed, carryingthe transferred image, through fusing apparatus 35 wherein the copy ismade permanent and is then fed onto roll 36. The movement of web 28 issynchronized with the turning of drum 10, which in this embodiment isrotated in a clockwise direction. The drum 10 and the web 28 may bedriven by a motor (not shown) or by other conventional means.

Although not shown in Figure 1, a cleaning device may optionally bepositioned along the path of rotation of xerographicrplate nextfollowing the transfer area to clean theplate surface prior to chargingor sensitizing. The cleaning mechanism may be a rotating brush orthe'like operating to remove any particles remaining on the platesurface after transfer.

In Figure 2 a more detailed drawing of development stage 21 is shown. AsinFigure 1 the drum is generally designated as 10, the developmentelectrode as '23, and the developer cloud supply as 22. As appears moreclearly in this figure, developer cloud supply 22 feeds developerthrough turbulence tubes 37 to manifold block 38 wherein-additional airsupplied by air supply 24 is mixed with the mixture of powder and airfed through tubes '37, the additional air carried by tubes 40 and-41being-mixed as-indicated in the-drawing. Although not clearly-shown inthis figure, tubes 37 extend across the width of photo-conductiveinsulator 12 ,(see Figure 3). The developer cloud is emitted frommanifold block 38 throughdevelopment slot 42.

In Figure 3 a detailed front view of development electrode 23 as itrelates to its supports, controls, and the drum 10 is shown. Manifoldblock 38 is permanently mounted over photoconductive insulator 1 2 sothat developer fed through tubes 37 and mixed with air fed through tubes40 and 41'will issue forth from development slot 42 (not shown in thisfigure) directly over the electrostatic latent image on the surface oflayer 12. A s1ot43 is provided in development electrode 23 to allowlaterial movement of electrode 23 while manifold block 38 remainsstationary and above sensitive layer 12. Shafts 45 ride through guidemembers 46 and 49 and act to support development electrode 23 at itsproper distance and position'during the course of movement of electrode23 through its cycles. Shafts 45 are permanently affixedto the frameworkof 'an automatic machine such as isshown in Figure 1. Screw 47 issupported bysupport bar 53 and the framework of the equipment (notshown) and is driven by motor 50 through belt "48. A sleeve 52 ispermanently afiixed to guide member 46 and -a hole is provided inguide-member 46'to allowmovement of screw 47 through-sleeve 52'and guidemember 46 while motor 50 is-operating. A pin51 extends from sleeve 52into grooves provided in screw'47 and causes lateral movement ofdevelopment electrode23 back and forth above drum 10. The rotation'ofscrew 47 -with--pin-51 fitted of screw-47. At an end pin 51 followinggrooves cut in screw 47 follows a new path reversing the direction of-movemeht of sleeve 52"thereby. causing the direction ofmovement-ofdevelopment electrode 23 to reverse. :This new'direction isfollowed until the'other 'end .of screw 47 is reached' at which point"the direction of travelis again reversed. In operation then, Whilescrew 47 rotates in one direction and does not otherwise move,development electrode 23 is constantly driven back and forth due to theaction of pin 51 in the grooves of rotating screw 47 over drum 10 whileguided and positioned by shafts 45. It is to be understood, of course,that mechanical systems other than the one shown will accomplish thesame results and are, therefore, intended to be included within thescope of this invention.

Figure 4 is a detailed side view showing the relation of developmentelectrode 23 to guide member 46. As previously indicated, shafts 45 passthrough guide member 46 and as is clear in this figure shafts 45 movethrough ball bearings formed for linear travel or ball bushings 55, andopening 56 is provided in guide member 46 to allow screw47 to move backand forth through guide member 46. As previously indicated, shafts 45are permanently affixed to the framework of the equipment and because ofthe permanent position of ball bushings 55 it may be be said that guidemember 46 'is moved through a fixed area. Development electrode 23 isconnected to guide member 46 by the three screw assemblies 57, -8 and 60which allow for adjustment of the spacing of development electrode 23 asit relates to guide member 46. Adjusting spacing between the guidemembers 46 and development electrode 23 also adjusts spacing betweenlayer 12 and development electrode 23 in that drum is, as are shafts 45,permanently aflixed to the framework. As sembly 58 is formed as a partof development electrode 23 and allows movement along the screw lengthof the assembly. Assemblies 57 and 60 also allow adjustment along thescrew length, but in addition allow for the'new angles which will becreated by connecting the screws of these assemblies to developmentelectrode 23 so that they may pivot slightly in either direction asadjustment takes place. 7

It is noted that a detailed view of guide member 49 would appear thesame as guide member 46 in Figure 4 except that opening 56 would not bepresent. As indicated in Figure 3, screw 47 does not extend to orthrough :guide member 49. It is further pointed out that other:mechanism able to accomplish what is accomplished by the mechanism ofthis figure is intended to be encompassed by this invention.

In Figure 5 a top view of cleaning means generally designated 61 as itis positioned in relation to development electrode 23 and drum 10composed of photoconductive insulating layer 12 and conductive backingmember 11 is shown. As is clear in this figure, cleaning means 61projects to conductive backing member 11 of drum 10 but is spaced aparttherefrom. Cleaning means 61 in this embodiment is composed of brushes62 and 63 extending outward from axle 65 and positioned to contact allareas of development electrodes 23 which move into position above them.Also extending outward from axle 65 are pinions 66 and 67 and extensionarms 68 and 70. Extension arm 70 is fitted at its end with guide wheels71 which act to position in place pinion 67 along the rack in which itsteeth ride. The combination of pinion 67 and guide wheels 71 connectedthrough extension arm 70 and axle 65 also acts to support cleaning means61 in its proper plane during the cleaning cycles. Similar provisionsare made for pinion 66 through extension arm 68 and guide wheel 72 andthis group also supports and aid in positioning cleaning means 61.Extension arm 68 is also fitted with a freely rotating set of sprocketwheels 73 and these act to properly position a chain which rides oversprocket 74 and which drives cleaning means 61 along racks provided aswill be discussed more fully below.

In Figure 6 is shown a detailed view of the mechanism for drivingcleaning means 61 shown in Figure 5. This mechanism acts to drivecleaning means 61 (not shown) through pinion 66 which is positioned atthe outer edge of cleaning means 61 as is shown in Figure 5. As waspreviously indicated in the discussion relating to Figure 5, and asappears more clearly in Figure 6, pinion 66 moves along rack 75 and isheld in place on rack 75 by guide wheels 72. Also, as has beenpreviously indicated and as appears more clearly in this figure, freelyrotating sprocket wheels 73 act to position and hold in place chain 76which passes around sprocket wheels 73 and over sprocket 74 to drivepinion 66 along rack 75. A reversible motor 77 drives the assemblythrough belt 78 connected to sprocket wheel 80. Sprocket wheel 80 alsoacts to supply a path for drive chain 76 at a point beyond rack 75. Thislatter function of sprocket wheel 80 is the only function of sprocketwheel 81, a freely rotating wheel positioned at a point beyond theopposite end of rack 75. Switches or microswitches 82 and 83, near eachend of rack 75 and within the path of movement of guide wheels 72, areconnected to reversible motor 77 through a box including timers andrelays to bring motor 77 to a stop before it is rotated in the oppositedirection. When a microswitch 82 or 83 is operated by a guide wheel 72striking switch element 85 or 86 the direction of motor 77 is reversed.When motor 77 is reversed belt 78 drives sprocket wheel 80 in theopposite direction causing chain 76 to reverse the path of movement ofpinion '66 along rack 75. Since rack 75 is shaped to provide a path forpinion 66 which will cause brushes 62 and 63 to ride against the surfaceof development electrode 23 movement up and down of pinion 66 along rack75 causes brushes 62 and 63 to sweep the inner circumference ofdevelopment electrode 23.

Although slack is to some extent desirable in mechanism driven by achain, in the mechanism shown in Figure 6 the amount of slack in chain76 will vary due to the different position along a curved surface ofpinion 66. Assembly 87 comprising two freely rotating sprocket wheelsare mounted on a shaft centered between them. This assembly is free torotate about this shaft and a torsion spring is provided to rotate theassembly to take up slack in drive chain 76 thereby insuring the properamount of slack in chain 76 at all times during a cycle of movement ofpinion 66.

To further clarify the action of pinion 67 shown in Figure 5, it isnoted that it moves along a rack exactly like rack 75 which is connectedas is rack 75 to the framework of the equipment. Guide wheels 71 shownin Figure 5 act to position and hold in place pinion 67 along its rackas guide wheels 72 act to position and hold in place pinion 66 alongrack 75 shown in Figure 6. The combined action of the two separatedracks operating on pinions 66 and 67 hold cleaning means 61 in aposition which is perpendicular to the outer edge of drum 10 during itsup and down rotating movement against development electrode 23. Pinions66, 67 and sprocket 74 are permanently affixed to axle 65. As cleaningmeans 61 is made to move due to the action of chain 76 on sprocket 74cleaning means 61 is both rotated and moved either up or down along theracks provided for pinions 66 and 67 to ride in. The combined movement,that is the rotation of the brushes 62 and 63 and the displacement upand down, while brushes 62 and 63 are in position to contact areas ofdevelopment electrode 23 cleans the surface of development electrode 23.

The cleaning mechanism which has been described and illustrated inconnection with Figures 5 and 6 is duplicated on both sides of drum 10with brush 63 at the outer extremity in both instances and the cycle ofmovement of development electrode 23 includes extending outward to theouter edge of brush 63 on each side. The mechanism shown and describedis for illustrative purposes and mechanism generally able to guide andclean as does the mechanism of this embodiment is intended to beencompassed by this invention.

Although the apparatus has thus far been described in terms of a numberof components it is to be understood '7 that these components actingtogether form an integrated mechanism. This point will appear moreclearly as the overall operation is further examined.

In automatic machines adapted for continuous operation and especiallysuch machines adapted for continuous tone reproduction, it is desirableto space the development electrode at a very slight distance as forexample from .1 to .001 inch, from the photoconductive insulating layer.Development electrodes 23 of this embodiment of the invention is spacedto be adjusted by screw assemblies 57, '58 and 60 within this range. Thedevelopment electrode itself should be composed of any dimensionallystable conductive material as for example steel, brass, aluminum and thelike,'and should be polished so as to present a smooth, even,equidistant surface to the photoconductive insulating layer which inthis embodiment is layer 12.

Development electrode 2.3 is formed having a width slightly more thantwice the width ,of .drum For example, if a drum 6 inches in widthisbeing used, it would be desirable to use a development electrode witha width of approximately 14 inches. During development of theelectrostatic latent image, some portion of the development electrodealways appears .above the photoconductive insulating layer beingdeveloped. The action of cleaning means 61 While an image is beingdeveloped is to clean thoseareas of development electrode 23 extendingoutwardly'from either or both sides of drum 10. Cleaning of the outerextremities of development electrode 23 is assured in that cleaningmeans .61 will go through a number of cycles during the time ,an edgetakes to extend outward from drum 10 to its furthest extended positionand to return to above dmm 10 again. To insure cleaning of all areas ofdevelopment electrode 23 at least once during its cycle of movement itis desirable to allow more than half of development electrode 23 toextend outward :on ,each side of drum 10 during a cycle of movement. In.so doing cleaning of the center area as well as all other areas ofdevelopment electrode 23 is assured since the central zone is extendedinto the cleaningarea twice during the cycle-of movement of electrode 23.and also because the area of the central Zone which :is extended thesmallest distance onone-side of drum 10 is ,extendedthe greatestdistance on the other side. Further provisions may be made to insurecleaning of this centralzone as for example providing that cleaningmeans 61 move through a cycle in less time thanit takes for thedevelopment electrode to move that distance which .makes up the centralZone which is extended on both sides for cleaning purposes.

The time it takes for the movement of cleaning means 61 through itscycle is. controlled by motor 77 and the distance cleaning means 61must. travel. In the embodiment shown a cycle of approximately 24seconds in duration has beenused to clean an electrode 23 of 13 inchesalong its inner circumference. The preferred cycle relates to the widthand cycle time of development electrode 23 which in this embodiment is14 inches and less than 2 minutes. in this embodiment cleaning of thecentral area at least once during each cycle of movement of developmentelectrode '23 is assured.

The height of the development electrode should be such that loss ofdevelopment cloud through'the top and through the bottom is effectivelyprevented and the development slot 42 should be positioned as near tothe center as is possible. As appears in Figure 3 development slot 42does not extend across the entire width of development electrode 23- andthis is a limitation. of movement of electrode 23. While the equipmentis in operation it is necessary to supplydev'eloper cloudthroughdevelopment slot 42 above all ,areas of the photoconductiveinsulating layeri12 and therefore asurface suchas developmentelectrode,23 cannot be interposed between slot 42 and layer 12. Inoperation then, when one end of development slot 42 reaches manifoldblock 38, the direction of movement of development electrode 23 isreversed. In order to keep the overall width of development electrode 23to a minimum it is desirable to form development slot 42 with a maximumof coverage across the width of electrode 23. It is to be understood, ofcourse, that an electrode may be formed of two members separated by adevelopment slot and mounted on suitable supports, and this invention isintended to include such an electrode within its scope.

Cleaning means 61 shown in Figure 5 is composed of brushes 62 and 63separated by pinion 6'7 and extension arm 7.0 mounted on a portion ofaxle 65. It is noted that whereas brushes 62 and 63 and pinions x67 and66 are permanently afiixed to axle 65, extension arms 68 and 79 areallowed to rotate freely. As has been previously indicated, pinions 66and .67, pinion 66 at an extremity of cleaning means 61 and the otherbeing separated from pinion66 and near the other extremity, are affixedto axle to drive cleaning means 61 along its path of movement whilerotating and while held in its proper position in respect to drum 1t anddevelopment electrode 23. Means have not been devised to date to clean adevelopment electrode spaced within the preferred distances from aconductive insulating layer 12 which extend and effectively clean withinthis narrow area. It has, therefore, become necessary to clean as shownin this embodiment inan area extending outward from drum 10; Complyingwith the .desire to keep the electrode to a minimum width, brush 62 hasbeen provided to clean development electrode 23 as close to drum 1% asis reasonably feasible. A preferred spacing between brush .62 and drum10 of from to A of an inch exists in this embodiment. A minimum ofspacing has been found necessary in order to insure proper insulationbetween drum 10 and its components, the brush and development electrode23. i

A variety of materials have been found to work well as material forbrushes 62 and 63, as for example, synthetic fiber material such asnylon, cellulose derivatives and the like and natural fibers such ascotton, wool, hair, furs and the like. Brushes composed of nylon fibershave been'found to work particularly well with steel electrodes. Thefibers should be dense enough to clean effectively, yet nottoo dense soas to clog with developer particles, and they should be fine enough toclean effectively and not too fine so that matting is avoided, yet thickenough to be durable and not too thick so that sufficient flexibilityofthe fibers is present and so that abrasion of the developmentelectrode surface is avoided. Contact of the bristles with the surfaceof development electrode 23 should be a sweeping brushing form ofcontact, one which is effective in removing deposited particles and yetcontact which does not actto brake the movement of the developmentelectrode.

Although this invention has been described in terms of cleaning means 61composed of brushes 62 and 63,.it is not intended in any way to limitthis invention to the particular embodiment shown, but it is intended toen compass within the scope of this invention all forms of cleaningmeans which can effectively accomplish the cleaning of all areas ofdevelopment electrode 23 during its movement through a cycle. Forexample, cleaning means comprising-bristles mounted and shaped likethose of a broom extending across the entire extended area of adevelopment electrode when fully extended, and connected to a rocker armwhich is driven to cause the bristles to move back and forth across theheight of the development electrode and which is adjusted to effectivelyclean the vdevelopment electrode during the sweeping cycle willaccomplish what cleaning means 61 accomplishes .and is, therefore,intended to be included within the, scope of this invention.

Experimentation hasshown that cleaning ofall areas of developmentelectrode 23 should take place at least once every four minutes whencontinuous development is carried on and preferabiy more often. Althougha coating of developer particles is formed within these time intervalsthis coating has not been found to detrimentally affect the imagedeveloped on layer 12. Regulation of the cycle of movement ofdevelopment electrode 23 is accomplished by controlling the speed ofmotor 48 which drives screw 47, the length of screw 47, the pitch of thegrooves of screw 47, and the like. In the apparatus shown in thedrawings a cycle of time of less than two minutes has been used. Thisfurther insures a clean development electrode 23 in that the cycle isrepeated twice during the period in which one cycle should be completed.

The cleaning process and apparatus while in operation fills thesurrounding area with developer particles removed from the surface ofthe development electrode. To protect other mechanism which may be apart of the xerographic apparatus shown in Figure 1 or other mechanismin the area and to protect an operator who might be near the equipment,it is desirable to enclose the cleaning apparatus. The enclosed areapreferably is also subjected to a slight negative pressure due to theaction of a vacuum creating system which acts to draw out of theenclosed area particles not deposited on the plate and patricles whichhave been removed from the surface of the development electrode. It isalso felt that this vacuum system aids in keeping the brushes ofcleaning means 61 free of removed particles.

Although this invention is applicable to all fields of xerography, it isespecially valuable in connection with continuous tone reproductionswhere its present need is greatest. A development electrode within thespacing requirements discussed in this invention may be used in mostapplications of the art of xerography. It is presently felt thatcritical narrow spaces as disclosed herein are required for continuoustone work. Since the cleaning mechanism of this invention is intended toeffectively clean the closely spaced electrode, it naturally finds itsreal value in that application of Xerography having the greatest needfor such spacing.

The close spacing between development electrode 23 and layer 12 acts tobring developer cloud in a highly dense state close to the platesurface. Since the elec trostatic field which causes developer particlesto deposit on the plate surface is related to the spacing between thedevelopment electrode and the plate, intense fields are created usingspacing as described in this invention. The combination of the densecloud and the intense fields results in high quality distortion-freequickly developed reproductions.

While this invention has been described in terms of a specificembodiment, in terms of an embodiment including a rotating drum as theXerographic plate member, it is to be understood that it is intended toinclude within the scope of this invention xerographic plates havingother forms such as flat xerographic plates and the like. It is alsointended to include within the scope of this invention other forms ofdrive means for development electrode 23, other shapes of developmentelectrodes, means other than as shown for driving cleaning means 61,cleaning means other than cleaning means 61, and the like, which areable to accomplish the ends achieved by the particular elements shown inconnection with the embodiment that has been described.

It is intended to cover the invention described herein as broadly as theart will permit, within the spirit and scope of the appended claims.

What is claimed is:

1. In a xerographic apparatus of the type in which a Xerographic plateof predetermined width moves in a path through a developing stage wherean electrostatic latent image formed on the xerographic plate isdeveloped by a developing material; a development electrode system forsaid developing stage including a development electrode having a lengthequal to at least twice the width of said xerographic plate, mountingmeans con-' nected to said development electrode to position saiddevelopment electrode in closely spaced relationship to said xerographicplate, said mounting means permitting movement of said developmentelectrode normal to thepath of movement of said xerographic plate,electrode moving means connected to said development electrode formoving said development electrode to a first posi' tion in which atleast a first half of said development electrode is in a non-operativerelationship to said xerographic plate and a second position where asecond half of said development electrode is in a non-operativerelationship to said Xerographic plate, and electrode cleaning meansoperatively connected to said development electrode for cleaning excessdeveloping material from said first half of said development electrodewhen it is in said first position and for cleaning excess developingmaterial from said second half of said development electrode when it isin said second position.

2. In a xerographic apparatus, the combination comprising a Xerographicplate, a development electrode means at least equal to the Width of saidxerographic plate, mounting means connected to said developmentelectrode means to position said electrode means in closely spacedoperative relationship to said xerographic plate, said mounting meansincluding means to permit movement of said electrode means relative tosaid plate, developing means operatively connected to said developmentelectrode for supplying a developing material to said xerographic plate,driving means connected to said development electrode means forselectively positioning at least a portion of said development electrodemeans into or out of operative relationship with said xerographic plate,and cleaning means operably connected to said development electrodemeans for removing deposited developing material from the portion ofsaid development electrode means not in operative relationship with saidxerographic plate.

3. In a xerographic apparatus including a xerographic plate mounted formovement through a plurality of processing stations, a developmentelectrode at least equal to the Width of said xerographic plate,mounting means connected to said development electrode to position saiddevelopment electrode in closely spaced operative relationship to saidxerographic plate, the improve ment including means forming part of saidmounting means for permitting movement of said development electroderelative to said xerographic plate, driving means connected to saiddevelopment electrode for moving said development electrode relative tosaid plate, whereby at least a portion of said development electrode ismoved out of operative relation with said plate, means connected to saiddevelopment electrode for supplying developing material to saidXerographic plate, and cleaning means operatively connected to saiddevelopment electrode for cleaning excess developing material from theportion of said development electrode that is moved out of operativerelation with the plate.

4. In a xerographic apparatus having a xerographic plate mounted formovement through a developing stage where an electrostatic latent imageformed on the Xerographic plate is developed by a developing material, adevelopment electrode having a width at least equal to that of theXerographic plate, mounting means connected to said developmentelectrode to position said development electrode in closely spacedoperative relationship to said Xerographic plate, the improvementcomprising means forming part of said mounting means for permittingmovement of said development electrode relative to said plate, drivingmeans connected to said development electrode for moving saiddevelopment electrode relative to said xerographic plate, whereby atleast a portion of said development electrode is moved out of;

11 opei'ative relation with said plate, and brush cleaning meansoperatively connected to said development electrode tor cleaning excessdeveloping material from the portion of said development electrode thatis moved out of qperative relation with the plate.

5. In a Xerographie apparatus of the type in which a cy i dr cal em apie plate o p edete mi ed d h. mo es i a p h o h. a e pi g stage W er anlect sta q atent imag f ed on the'xe o ph c plat is developed by adeveloping material, a substantially rigid eleetrieally conductivedevelopment electrode in form of an arcuate plate positionedconcentrically with said terographic plate, and mounting means (2011-neste to s d develop nt elec o to po iti n id de: el mem e ec ro c elyspa ed c nt ationship to said xerographic plate, the improvement incldmg connections in said mounting means for permitin mov ment oi sa d deveopm c o n m o the path of movement of said plate, said developmentelectrode having a width at least twice the width of said xerographicplate, electrode moving means connected to said development electrode tooscillate said development electrode across the width of saidXerographic plate, and electrode cleaning means positioned adjacent saidxerographic plate to contact said development electrode when oscillatedby said electrode moving means to clean deposited developing materialfrom said development electlgdfl.

6. In a xerographic apparatus of the type in which a cylindricalxerographic plate of predetermined width moves in a path through adeveloping stage where, an electrostatic latent image formed on thexerographic plate is developed by a developing material, an electricallyconductive development electrode cooperating with said xerographicplate, and mounting means connected to said development electrode toposition said develop? ment electrode in closely spaced concentricrelationship to said xerographic plate, the improvement includingconnections in said mounting means for permitting movement of saiddevelopment electrode normal to the path of movement of said plate, saiddevelopment ele ctrode having a Width at least equal to the width ofsaid xerographic plate, electrode moving means connected to saiddevelopment electrode to oscillate said development electrode acrosssaid Xerographic plate, whereby at least a portion of said developmentelectrode is moved out of operative relation with the plate, and brushmeans positioned adjacent said xerographic plate to contact the portionof the development electrode that is moved out of operative relationwith the plate when oscillated by said electrode moving means, wherebyto clean deposited developing material from said development electrode.

References Cited in the file of this patent UNITED STATES PATENTS 9 e by-,-.----s-.-= .--s=- y v 19 6 1,057,073 Mertens Mar. 25, 1913 1,549,875H nfi ----v----.-. ,-v---- 8 1 25 1,689,163 Suker-t Oct, 23, 19282,357,809 Carlson Sept. 12, 1944 2,509,276 Ransburg et al. T May 30,1950 2,551,582 Carlson May ,8, 1951 2,586,014 Dunphy Feb. 19, 19522,588,675 Walkup et al o- Mar. 11, 1952 3 79 Pethick Apr- 7, 195.32,643,087 K e ,--T Au 19 2,693,609 Briceno Nov. 9, 1954 2,701,764-Carlson Feb. 8 1955 21 561 Steinhilper V V V July 31, 19,56,

